(a) Field of the Invention
The present invention relates to a valve train for a diesel engine, and in particulars to a valve train arranged together with a dual overhead camshaft (DOHC) type cylinder head structure capable of being adopted by an engine having small cylinder bores.
(b) Description of the Related Art
Recently, to enhance energy efficiency and reduce exhaust gas emissions, direct injection-type high performance diesel engines have been equipped in vehicles. Furthermore, research and development on small passenger cars equipped with direct injection engines having low engine displacement, below 1000 cc, is active all around the world in order to comply with emission regulations and energy savings. To achieve these goals, various high technologies such as common rail fuel distribution, turbo chargers, and intercooler systems have been adopted by small passenger cars. FIG. 6 shows a part of a cylinder head 112 of a single over head camshaft (SOHC) engine having small cylinder bores, which is formed having intake and exhaust valves 114 and 116, a skew-installed fuel injector 118, and a glow plug 120.
As explained above, the SOHC engine of a 2-valve per cylinder valve train is disadvantageous relative to the DOHC engine of a 4-valve per cylinder valve train in the view of air intake, symmetrical swirl, high combustion rate, and so on.
Although the DOHC type cylinder head can be a solution to these problems, it is difficult to install the DOHC type valve train on an engine with a small cylinder bore.
The present invention has been made in an effort to solve the above problems of the prior art.
It is an object of the present invention to provide a 4-valve per cylinder valve train arranged with the DOHC type cylinder head capable of mounting on a DI diesel engine having small cylinder bores for enhancing fuel mileage, engine performance, and emission reduction.
To achieve the above object, a valve train for a small size diesel engine according to the present invention comprises a pair of camshafts rotatively supported by and passing over the top of a cylinder head, one pair of intake and exhaust cams on each camshaft for each cylinder, two intake ports and two exhaust ports formed on the cylinder head over and around a bore center of each cylinder for communicating with the cylinder bore, two intake valves and two exhaust valves installed into the corresponding ports for selectively opening and closing the ports, rocker arms of which one end of each is connected to upper ends of the corresponding valves, and lash adjusters connected to other ends of the corresponding rocker arms for adjusting lash between the rocker arms and the cams, wherein the intake and exhaust ports are arranged in an alternative zigzag fashion.